On the web the site says that you are allowed, I think it is 5 votes. At least it did. It counts them down for you. This is because there are multiple dance couples. This may have change since there are only 3 now but it may not have. Look carefully at the page where you vote and it will tell you.
I think since there are three couples, you get 4 votes. Last week 4 couples got 5 votes.